Synchronous bomb sight



April 14, 1931. AN 1,800,931

SYNCHRONOUS BOMB SIGHT Filed Oct. 11. 1928 e Sheets-Sheet 1 April 14, 1931. DUGAN 1,800,931

SYNCHRONOUS BOMB S IGHT Filed Oct. 11. 1925 6 Sheets-Sheet 5 J. DUGAN 31 SYNGHRONOUS BOMB SIGHT Filed 001;. 11, 1928 6 Sheets-Sheet April 14, 1931.

April 14, 1931.

J. DU GA N SYNCHRONOUS BOMB SIGHT 'Filed Oct. 11, 1928 6 Sheets-Sheet 5 mmL QWW MN Patented Apr.- 14, 1931 J'OSEPH DUGAN, 01; LOS ANGELES, CALIFORNIA SYNOHRONOUS BOMB SIGHT Application filed October 11, 1928. Serial No. 811,888.

This application is a continuation-in-part of my copending application Serial No. 29,843, filed May 12, 1925, which in turn is a continuation-in-part of my application Serial No. 746,238, filed October 27, 1924. and abandoned in favor of application Serial No. 29,843 on September .1, 1926.

The inventions disclosed in all three ap plications relate to bomb sight apparatus of the pilot-directing synchronous type and designed to effect the dropping of bombs from aircraft on targets on the earths surface.

The present invention is particularly designed to control the dropping of bombs on targets, fixed or movable, without the necessity of determining 'ground speed or speed relative to the target.

Other objects of the invention will become apparent as the detailed description thereof proceeds.

In the drawings:

Fig. 1 is a diagrammatic perspective sketch illustrating the corrections involved in the use of this apparatus;

Figure 2 is a diagram illustrating the underlying principles involved in the operation of this invention;

Figure 2a is a dia ammatic lan view of several parts of the invention, s own in dif- 39 ferent positions to illustrate the operation of these parts in determining essential corrections;

Figure 3 is a vertical section of the sighting part of this apparatus, taken on the line 3-3 of Fig. 4;

Figure 4 is a plan view of the sighting part of the apparatus shown in Figure 3;

Figure 5 is a side elevation of the sighting device shownin- Figs. 3 and 4, with the support for the said device shown in section taken on the line 5-5 of Fig 4;

Figure 6 isa perspective view of one of the correcting elements used in the sighting de- V Figure l is adetail showing the details of construction of arts of the correcting mechanism shown in igs. 5 and 6; A

Figure 8 is a; horizontal section taken on the line 8-8 of I re 7 Figure 2 is a retail section through the sight part of the device at its pivotal con nection to the sight-carrier elements;

Figure 10 is a fragmentary side elevation through the telesco e and its carrier, which is shown partly bro en away and in section;

Figure 11 is a side elevation of the telescope and its carrier; 7

Figure 12 is a central vertical section V through a pilot director forming part of this invention; i

Figure 13 is a section taken on the line 13-13 of Figure 12; a

Figure 14 is a plan of the pilot director with parts broken away to show interior details of construction; J

Figure 15 is a section taken on the line 15-15 of Figure 13;

Figure 16 is a somewhat diagrammatic plan view of a timing apparatus forming part of this invention; 1

Figure 16a is a section taken on theline lilo-16a of Fig. 16;

FFig'lre 17 is a section on line 17-17 of igure 18 is a horizontal section on the line 18-18 of Figure 17;

Figure 19 is a vertical section on the line 19-19 of Figure 18;

Figure 20 is a side elevation of the timing 1 apparatus shown in Fig. 16, parts being so broken away to illustrate details of construction more clearly;

Figure 21 is a vertical section taken on the line 21-21 of Figure 16;

Figure 22 isa section taken on the line 22-22 of Fi re 21; s

Figure 23 1s a vertical section taken on the line 23-23 of Fi re 20;

Figure 24 is a oriz'ontal section taken on the line 24-24 of Figure 20;

Figure 25 is ii-diagrammatic layout of the o apparatus as a whole;

Figure 26 is a side elevation of an electrical repeater connected to areversible motorv which acts as a relay to transmit rotary 95 movements of the re ater to other mechanism and at the same tune compensates the rov tor;1 of the repeater for friction oif its bearing; an r Figure 27 is a fragmentary plan view of 1 mg on a onto a target on the earths surface. The tri- 2 angle ABC is a triangle of velocities, in

which AB represents the air-velocity of the aircraft, BC represents the rate of movement of the atmosphere relative to the earth,

. ouslyre resents t.

and AC represents the resultant of theV airvelocity and atmosphere rate of movement wind) relative to the earth.- The (resultant G is commonly known as the track of the aircraft, and represents the direction of movement and speed of the aircraft relative to the earth; or, in other words represents the ground speed of the craft.

v While the bomb is carriedby theaircraft,

it is really a part of the craft; and. is subject to the same forces. is released from'the craft, it is subjected'to the resistance of the air, and this resistance causes a lag both in time of fall and in range of the dropped bomb.

theforces acting on the bomb as soon as it is released from the aircraft. The vector C'D represents the horizontal component of the air resistance to the bomb, and obviously must be set of! parallel to the airspeed vector AB or A'B', the vectors AB and A'G' and B'G' being merely the vectors AB, AC, and BC translated to the earths surface. The resultant A'D obvie velocity of the bomb relative to t e earth, under the conditions of air and wind velocities represented by the vector dialgrams. I p 0 those skilled in this art, the perpen dicular distance LD between the vertical plan e the earth, is known track plane-of movement of the craft over as the offset. The line A'D represents the range of the bomb. the line C D represents the trail thereof,.and the angle DOC representsthe trail angle.

So far as the present invention is con cerned, the plane EFGH is the vertical reference plane to which all measurements and dimensions are referred. When the craft moves up or down wind, the vertical plane therethrough in the line of flight includes the line JK; but is off-set from this line only when cross winds and/or the relative velocities of the craft and target cause drift of the craft toward the target. It is therefore necessarjys, for timing urposes, to resolve the range A and trail 'D into components at right an Ice to each other with one com onent of eac lying in the reference plane FGH.

From inspection of Figure 1, it is obvious that r sin a and 1' cos a are the components of the trail C'D, where 1 represents the trail and A trail, by the As soon as the bomb 1 represents the angle of drift of the craft. It is also clear that rain 01 represents the offset of the reference plane from the target D and that r cos' a is the component of the trail 1 lying in said plane.

All the settings in this invention are linear, and reproduce in miniature the bombing conditions asthey exist in space. In Figure 2, the triangle MNPis assumed to lie in the track or reference plane, and the target N is assumed to move horizontally along the line NP toward the vertical line MR dropped from the aircraft at' M. The sight is assumed to rotate about a horizontal axis at-M perpendicular to the reference lane and in synohromsm with the relative inear movement of. the target N toward line MR. The

range is represented by the line OP, and the line RP. Under these condi- .tions, it is obvious that if any point N be taken on the line of sight MN, and moved with said line horizontally toward the trail line MP, it will reach the point 0' at the same instant as the target itself reaches the point 0, which is the beginning point of the range of the bomb. The bomb will strike the point P at the instant when the sight The polygon A'B'C'D is a vector polygon r representing line and target coincides with'the trail line MP, and the point N will have moved to the point P. So far as this invention is concerned the range is to be considered as including the entire horizontal distance traveled by the bomb during its time of fall, and includes the trail of the bomb as a partof the range.

The range OP corresponds to the range component AL of Figure 1 plus the trail component LC, and the trail RP corresponds to the trail component LC of Fig. 1. These full size components have to be reproduced in miniature at the height of the'aircraft above the target. Therefore, in the inconnection with the elements designed to effeet the settings. I

The apparatus comprises (see Fig. 25 A sighting instrument S; a timer T' a sta ilizing gyroscopic pendulum Gy; director PD. The structural details o the gyro form no part of the resent invention; it isof standard construction throughout. The sighting instrument (see Figs. 3 to 11, inclusive) com rises an outer imbal ring 1 supported by t e diametrically o posite trunnions 2 and 3 in standards 4 an 5, respectively. The trunnion 3 is rigidly conand a Hot to the supporting base plate 8 of the standard 5. The repeater 7 is operated by the transmitter 9 (see F ig. 25) to maintain the outer ring 1 constantly parallel to the outer gimbal ring 16 of the gyro which is pivotally supported by trunnions 11 and 12 in the standards 13 and 14, respectively.

A bail 15, (Fig. 25) of the usual type, is pivotally supported by the trnnnions 16 and17 in the standards '18 and 19, respectively; and the trunnion 17 is rigidly secured to the rotor shaft 20 of the transmitter 21 which is electrically connected to the repeater 22 of the sight apparatus. The repeater 22 has its rotor shaft passing through slot 23 (Figs. 4 and 5) in the standard 24 which projects up from the bracket 25, fixed to the nose 26 of the aircraft, and secured to the arcuate channel plate 27 to maintain this plate 27 at the same angular position in space as the bail 15 of the gyro.

The inner gimbal ring 28 (Fig. 4) is pivotally supported by trunnions 29 and 30 in the outer ring 1, and an arcuate plate 31 fixed to the trunnion 29 slides in the channel of plate 27 to maintain the ring 28 constantly horizontal.

The ring 28 has a flange 32 extending inwardly from its lower edge to form a fixed stabilized horizontal support for the sight standard. The suspending base of the standard is formed by side members 33 and 34 Fig. 3) connected by ends 35 and 36 (Fig. 4) to form a rectangular base from which lugs 37, 38, 39 and 40 proj'ect to seat-'slid'ably on the flange 32. A gear 41 is secured suitably to the top of this rectangular base and rotates therewith on the flange 32 of the inner ring 28. A bridge 42 is securely fixed at its opposite ends to the ring 28 and serves to hold the rectangular sight base and gear ring in position in the recess formed by the ring 28 and its flange 32.

The center line of the bridge 42 must coincide with the diameter of the ring 28 which must be fixed'parallel with the keel line of the aircraft, and the bridge must be fixed so as to allow the ring gear and the sight base to rotate freely thereunden. The bridge 42 at its center is provided with a slot 43 in which slides a trail angle adjusting plate 44 providedwith an indicator 45 reading on a trail angle scale 46. The plate 44 slides on flanges 47 and 48'projccting from the sides of the slot 43, and is centrally apertured to receive rotatably the shank 49 of a bolt 49' (see Figure 7) which is screw-threaded at its upper end to receive the nut 50 which acts as a clamping nut for securing the plate 44 in ad justed position on the bridge 42.

The bolt 49' is shouldered to form a seat for the lower clamping plate or washer 51 which slides below the flanges 47 and 48 to cooperate with the plate-44 and bolt 49' and plate in securing the bolt in adjusted position; and the lower end of the bolt is reduced to form a pivot )in v52 on which is rotatably mounted a mom )CI' 53 having arms 54 and 55 arranged at right angles to eaclrother (see Figures 6 and 8).

Cylindrical rods 56 and 57 (Fig. 6) project from the" arms 54 and 55, respectively, and are slidably mounted in guides 58 and 59, respectively. The guide 58 slides rectilinearly in aslot 60 formed in the front end 35 of the standard (see Fig. 3) and is slidably held therein by means of a lock nut 61 (Fig. 5) and a flange 62 formed on the rear of the guide (Figure 7). A boss 63 projects rearwardly from the guide 58 and is provided with an annular groove 64 designed to receive slidably a pin 65 adjustably mounted on the upper end of a bearing 66 formed on the upper end of a sight controlling arm 67 (Fig. 3).

The arm 67 has its lower end slidably connected by the pin-and-slot connection shown in Fig. 3, to the upper end 68 of a bifurcated stirrup 69 having fin-cations 70 and 71 extending on opposite sides of the sight 72.

The sight 72 has a sleeve 73 (see Figs. 3, 10 and 11) secured thereto, and this sleeve 73 is rotatabl mounted in an outer sleeve 74 which is'provi ed at its opposite sides with slots 7 5 and 76 to slidably receive the pins 77 and 78 which project from the furcations 7 O and 71, respectively, in alinement with eachother to contact with the opposite sides of the sight 72'and form a pivot axis therefor. A pivot 79 is fixed to the lower side of-the sleeve 74 and projectsthrough an aperture 80 formed centrally in the sight supporting trunnion member 81 having its opposite ends rotatably mounted in the side members 33 and 34 of the sight suspending standard structure.

The trunnion member 81 is centrally bent to form a recess 82 in order to locate the sight so that its axes of rotation intersect in a point lying in axis of rotation of the member 81, and so that its four axes of rotation are concurrent.

The rod 56 slides perpendicularly through I the bore 87 formed in the guide 59 (see Fig. 4), and this guide slides freely in a slot 88 formed in the upper part of the side member 33. The guide 59 has a cylindrical boss 89 extending laterally from the side member 33, and this boss is provided at its outer end with a washer and lock nut 90 (Figure 5) designed to connect the upper end of an arm I 91 slidabl and pivotally, to boss 89. The

' feet whatever on the trunnion axis ber 33 with its axis of rotation-alined with,

but not connected to, the axis of the trunnion member 81. The'sole purpose of the arm 91 is to transmit thet rail correction to a repeater on the timer, and it does not have an efthe - sight 72. v

' The time? The timing mechanism is supported on anysuitable base 94 and as shown, is of the transmission type. This mechanism comprises a repeater 95 (see Figs. 16 and 26) connected electrically to the transmitter 92 of the sighting apparatus to re at the angular movements of the arm 91 a out the axis of the trunnion member 81.

Since the timing operation involvesgthe angular movement of comparatively heavy correcting mechanism, I have interposed a relay reversible motor 96 between there-- peater and this correcting mechanism which not only transmits this movement from the repeater, but also compensates the repeater for friction in its rotor bearing. As'ordinarily used, these repeaters include an indicator dial over which an indicator rotates. By this method of deriving power from the repeater, or similar instrument, a gear 97 (Fig. 26) is substituted for the usual indicator dial; and this gear 97 is rotatably mounted in the casing of the repeater in such manner as to form a bearing for the rotor shaft 98 of the repeater. Instead of the usual indicator, an arm 99 is fixed to the upper end of the shaft 98 and extends radially over the gear 97, on which, concentricall with the shaft 98, is fixed a pair of electrical contact,

segments 100 and 101 separated from each other b a thin plate of lnsulating material 102. e arm 99 has a small contact wheel 103 rotatably mounted on its outer end to travel over the contact segments 101 and 102, which are electrically connected to the fields of the reversible motor 96 to cause rotation of the motor shaft 104. and the gear 105 fixed thereto to make gear 97 follow the arm 99 and bring the insulating plate 102 directly under the wheel 103.

The follow-up operation of the reversible motor 96 and the repeater gear 97 is quite similar to the operation of the follow-up motor in causing the phantom ring of 'a gyrocompass to follow the gimbal ring SuIiPOI't for the giro. However, this princip e of operation as never been applied to the transformation of the ver weak movements of pointers of indicating mstruments into strong power movements, which also compensate the shaft in its bearings.

While I have shown this follow-upmethod of deriving directed power from the rotor of a repeater, it must be understood that this method may be used to convert the feeble rotary movements of the pointer shafts of delicate indicating instruments, such as airspeed meters and altimeters, into powerful rotary movements to be, applied wherever resistance is to be overcome, and wherever the translation of such. feeble movements in directed powerful movements is found necessary or desirable. In my copending application Serial Number. 383,402, filed August 3, 1929, I- have shown this method as applied to the trunnion axes of a yroscopic stabilizer. This particular part of t einvention isof very wide application and will be claimed accordinggy. a o

' eferring now to Figs. 16 and 20, the repeater 95 is operated by the transmitter 92 (Fig. 3) to cause the arm 99 to rotate in synchronism with the rotor of transmitter 92. This synchronous rotation sets the reversible motor 96 to cause the gear 97 to follow up the" movements ofthe arm 99. In causingthis follow-up movement of the arm 99 the motor gear 105 rotates through the same angle and maintains the trail-correcting arm 1 10,6 of the timer at the same angle plane indicated by the line 107 as the arm 91 makes with the vertical plane assing through the axis of the trunnion mem er 81.

A sleeve 108 slides lengthwise on the arm 106, and this sleeve has a' ivot 109 extending from the top thereof t rough a slot 110 formed in a support 111 fixedto the base 94 standards 112 and 113. The ivoted to the slide 114 which is on the support 111 by through the pivot 109 is guided recti inearl engagement with t e side walls 115 and 116,

of a recess 116 formed in the slotted part of su ort 111? I e slide 114 has one end u turned to form a bearing 117 (Fi rex16) in which is rotatably mounted a sha 118 having a long screw 119 coaxially secured thereto above the slot 110. A nut 120 is threaded onto the screw 119 and has a key 121 extending from the. bottom thereof into sliding engagement with a slot 122 formed in the up erface of the slide 114. A pin 123 exten s from the upper side of the -nut 120 and slidably engages the slot 124 formed in one end of a rod 125 havin its other end fixed to a vertical rod 126. he rod 126 is guided rectilinearly in a slot 127 formed in a support 128 fixed to the base 94 and has its lower end pivotally connected to the trail correcting am 106 to slide in a slot 129 formed therein (Fig. 16). The nut 120 must be adjusted so that the distance between the axis of pivot 109 and the axis of the gin 123 corres onds to a maximum speed of t to the reference lOl e aircraft re ative'to the tar get and arbitrarily selected as a constant for the purpose of calibrating the settings of theinstrument. -This distance corresponds to the instrument range setting Of P in the dia gram shown in Figure 2 and varies directly as the square root of the altitude of the air-- craft. Since thetrail arm 106 varies its pomechanism for setting the nut 120- re ardless of the movements of the arm 106. For this purpose, the shaft 118 extends slidably through a worm gear 130 and is keyed to said gear to be turned only by the rotation thereof and not by any relative sliding move,- ments between shaft and ear. The gear 130 is mounted to rotate in earings formed in the small standards 131 and 132 fixed on the support 111, and meshes with a worm gear 133 rotatably mounted instanda'rds 134 also fixed to en port 111. 1

The sha of'gear 133 .is fixed to the rotor of the range repeater R- r, which may be connected to a computer for determining the maximum range settings of the pin 123 rela" tive to the axis ofthe pivot 109. However this gear shaft maybe rotated manually or byany othersuitable means, as the drawin ismerely intended to show some means fixe to the slide support 111 for adjusting the pin 123 relative to the constantly sliding pivot pin 109.

On the rod 125 there is slidably mounted a slide 136 rovided with a slot 137 adapted to receive t e pin 123 and rod 126, in order to permit the said slide 136 to slide freely on the rod 125 above the upper ends of the pin 123 and rod 126. A pivot 138 extends rom theupper face of the slide 137 and is connected to a slide 139 slidably pivotalleg on abar 140 movable toward and mount from theslide sup rt 1 11 and constantly iie end of the bar 140 just the bar 140 towardand from and over the slide support 111.

The slide 139 has a pin 146 '(Fig. 21) projecting from the upper face thereof; and this pin 146 is pivoted to a slide 147 which extends around flanges 148 projecting in opposits directions from the lower edges of a bar 149. The up or side edges of the bar 149 are provided with laterally extending flanges 150 to receive the inturned flanges 151 of a slide 151'.

A pin 152 extends from the lower face of a slide 153 through a slot 154 in a fixed guide plate 156, and is ivoted to the slide 151';

on the plate156 by reason of its being seated to slide snugly in the recess 155 formed in the plate 156 on opposite sides of the slot 154. An electric contact 156' is fixed to the upper face of slide 153, and is connected suitably to the usual bombing apparatus to control the dropping of bombs.

It is to be noted that thepivot axes of the slides 136, 139 and 147 are coincident; and that the common pivot axis of the upper slides 151' and 153 is in alinement with "the:

face of the contact 156. Standards 157 and 158'support the plate 156 as well as the lower slidesupporting plate 111 in vertical alinement with each other.

The standard 158 is continued above the p plate 156, and supports one end of a long slidesupport 159, the other end of which is fixed to and supported by a standard 160 rising from the support 94.

" The bar 149 has its opposite ends provided with extensions 161 and 162, sliding, respectively, in grooves'163 and 164 formed on the o posite ends of a rectangular frame 165. btandards 167 and 166 have their upper ends suitablysecuredto the frame 165, and have their lower ends provided with flanges 168 and 169, respectively, for fixing said frame to the trail correcting arm" 106. The connection between the frame 165 'andthe arm 106 is such that the bar 149 is maintained in constant parallelism with the arm 106.

The upper guide plate 159 is provided with a slot 170 formed in a recessed seat 171 for an electric contact memberv 172 which projects through the slot 170 to be moved toward and from the contact member 156" and cooperate therewith in the control of the dropping of the bombs. A worm shaft 174-,

journaled in the standards 1 58 and 160, has a bevel gear 175 fixed to one of its ends and meshing with a bevel gear 176 on one end of a shaft 178. The shaft 178 is journaled at its opposite ends in a bracket 179 projecting laterally from the upper end of the shaft 158 and in a standard 180 extending up from the base support 94.

A spur gear 181 is fixed to the shaft 178 near the standard l80, and meshes with a similar gear 182 fixed to a shaft 183, which extends above and parallel to the worm shaft 142 and is journaled in the standards 180 and 184. The shaft 183 is square in cross section, and has the friction wheel 185 mounted to slide thereon and be rotated thereby. The yoke arms 186 and 187 extend around the shaft 183 on opposite sides of the wheel 185; and a stem 188 connects these arms 186 and 187 rigidly to the threaded boss 141.

The wheel 185 forms one element of a driven friction disk drive mounted suitably in a casing 189 suitably supported by the base 94, This friction disk drive includes a friction disk 190 rotatably mounted on ball bearings in the casing 189, and secured in said casing by a 190' with one face in drivin r iction contact with the edgeof the wheel 185 The disk 190 is rotated in the casing b a ball 191 mounted for free rotation in a rame 191' carried centrally by a screw 192 which is threaded into the casing 189 in order to effect adjustment of the ball 191 toward and from the center of the disk 190.

A driving disk 193 is mounted in the casing 189 parallel to the driven disk 190 and" in friction driving contact with the ball 191; and, this disk 193 is fixed to the rotor shaft of a constant speed motor 194. An indicator 195 extends laterally from one end of. the screw 192 over an altitude scale 196 to indicate the adjustment of the ball 191 for different speeds at different altitudes of the aircraft.

I A sight arm 197 (Figs. 16-and ,20) is detachab y secured by any suitable, type of clutch to the rotor of a sight repeater 198, or S a controlled by the sight transmitter St Fig. 3). to be moved infis ynchronism with sight 72. The 'arm 1971isprovided with a slot 199 to receive slidably. the small shaft 200 which has a. spring contact blade 201 fric-' tionall secured thereto by 'mean's'ofthe friction a justing set screw 202. An arm 203 projects from the hub 202' ofthe arm oItjcontact blade'201, and serves to maintain the j blade 201 just centered between the electrical 'contacts204 and 205, and normally out of contact therewith, for automatically control- 1 ling the operation of the reversible motor 145.

Suitable tension springer-and s have their ends secured to the opposite sides of the arm 203 and to set screws 207 mounted in standards 206 extending upwardly from the top of a gear casing 208 m which the shaft 200 is rotatably mounted; It will be evident from Fig. 16, that adjustment of the set screws 207 wi move the spring blade to any desired position of adjustment between the contacts 204 and-205.

The shaft 200 has a worm gear 175'Isecured thereto and in mesh with the worm shaft 174. A toothed ring 209 is fixed to this shaft 200 and is adapted. to be engaged by a toothed plate 210 mounted on the end of a rod 211-which is slidably mounted in the casmg 208. A knob 212 is used to facilitate the positioning of the rod 211 against. the

tension of the spring 212'; and a cross pin 213 cooperates with a slot 214 formed in the wall 215 of the casing 208 to permit the withdrawal of the late 210 from the toothed ring 209, and to ho' dthese members se arated by turning the pin 213 across the s ot 2.14, as shown 1n Fig. 19. f

Attention is articularlydirected .to the fact that the shafts 178 and 183 and theworm shaft 142 are parallel to each other and at right angles to the slide supports 111 and 159. The center of the slot 127 in the support 128 lies in the plane perpendichlar.

assumed. It is bar 1% to the pp rt 94and'containin theaxisf the shaft of motor 194',-in order t at the movable axis of the pin 126 may-be considered 1 I as the apex of a triangle, the sides of which are formed by lines joining the axis of the pin 126 to the axes of the pivot 109 andthe pin 123, and the base of whlch is formed by the line joining the axis of the pivot 109 to the axis of the pin 123.

The arm 106 is the trail correcting arm of the timer and corresponds in function to the diagrammatic trail arm MP of Fig. 2. The arm 197 is the sight controlled arm of the timer, and corresponds in function to them- 'tatable sight'line MN of Fig. 2. The line joining the axis of the pivot 109 to the axis of the pin 123 corresponds to the range scale line P'O' of Fig. 2.

therefore taken in order to make clear the principle involved in the timing part of this apparatus.

feet/sec. as the arbitra ly selected maximum relative speed; and a ing that the dis tance between the common axis a of the trail and si htarms and the center line passing Referring now to Fsig. 16, and taking 440 throug the axes of the pivot 109 and the pin 123 is one foot, it is first necessary'to set the pin 123 with its axisv at a distance from the .axis of the pivot pin 109 correspondin to the maximum ground or relative d o the craft toward the target. The dlstance between the axes just referred to varies directly as the uare root of thealtitude. This will be ObVlOllS from the fact that this distance is determined from the well known formula: 1 1

F W a where 8 represents the distance; a", the velocity; t, the time of fall; 71, the height; and, g the acceleration of gravity.

Taking the acceleration of gravity as equal to 32 feet per second, the times of fall from the heights 14,400 feet, 19,600 feet, and 25,600 feet are, respectively 30, 35 and 40 seconds.

Since the point N of the line of sight MN moves along the line NP at the rate of feet per second the, point N must travel along theline NP' at a speed whichvaries inversely'as the-height. For example. if the altitude be one thousandfeet the. int N would travel at one thousand o 440 feet per second ground speeda Now toget the distance of the pin 123 from the axis of pivot 109, when the bombing'is to be effected at an altitude of 14,400 feet, we must multipl the maximum ground speed by the time of fall-and divide the product by the altitude; that is, 440 feet multiplied by 30and' divided by 14,440, giving 11/12 feet or eleven inches as the settm of the pin v123 from the axisof pivot 109." imilarly, the settings for mum ground speed, and vary directly as the square root of the altitude; air speed and wind velocities have nothing to do with this maximum ground speed.

Reverting to Figs. 16 and 20, let it be assumed that the pin 123 has been adjusted to the required fixed distance from the axis of the pivot 109,. and that the arm 140 is in its upper dotted line position (Fig.16) so that the contact 156 is directly over the axis of the pin 123. If now, the worm 175' be locked to the casing208 and the worm shaft is rotated at a speed which would causethecasing 208 and the contact 170' to move at a speed of 440/h feet per see, the upper end of the shaft 200, sliding in the slot 199 would cause the sight arm 197 to rotate in synchronism with the sight line and the target. The friction drive and worm gearing must be designed to perform this particular function.

Conversely, if the worm gear 17 5' were free to rotate in its casing 208, and the worm shaft 174 were locked against rotation, it will beobvious that if the sight arm 197 were rotated under control of the sight itself it would cause the worm gear 17 5 to rotate and roll along the fixed worm shaft and would also move the contact 170' in synchronism with the sight toward the contact 156. If the worm gear 175' be unlocked, and the sight arm 197 move the shaft 200 and worm gear 17 5' insynchronism with the sight itself, and if theworm shaft 17 4 be rotated at such speed as to move the worm gear and shaft at the same synchronous speed toward the contact 156, it will be evident that the worm gear will be moved bodily, without rotation, along the rotating worm shaft 174; and the plate 201 will be held out of contact with the contacts 204 and 205. If now, the sight arm 197 decreases its speed of rotation, it wil retard the rectilinear movement of the shaft 200 and thereby cause anticlockwise rotation of the worm gear 175 and the shaft 200. This rotation will move the spring contact blade 201 into contact with the contact point 204, and thereby operate the motor 145 to move the friction wheel 185 toward the center of the disk 190 until the speed of the shaft 17 4 is decreased suficiently to move the shaft 200 (as if it were locked to the casing) at the same rate as the shaft is being moved by the sight arm 197.

The movement of the wheel 185toward the center of the disk 190 naturally moves the arm 140 away from the slide support 111, and this movement also causes the contact 156' to move toward the axis of the pivot 109. This is as it should be, because decrease in angular speed of the sight arm obviously carries with 1t a' corresponding decrease 1n theground speed of the bomb.

For example, if the relative speed of the aircraft and the target he one-half of the arbitrarily selected maximum speed, the contact 156 will be moved by the bar 149 to a point half way between the axes of the pivot 109 and the pin 123. Itwill be obvious from the geometrical construction of the elements, as shown clearly in Fig. 16, that as the angular speed of the sight arm 197 changes, the motor 145 will be automatically operated to movethe friction wheel 185, and the arm 140 along with it, until the parts'all move in absolute syncln'o11ism'; and the contact 150 will be automatically moved to the correct setting relative to the axis of pivot 109 for the changed relative speed conditions.

From the foregoingdiscussion, it will be obvious that the sight contact carrier 208 is moved by the sight arm 197 ata speed which varies inversely as the altitude of the craft, and also at a speed which varies directly with the horizontal velocity of the craft toward the target. In order to obtain the same con stant relative maximum speed at the various altitudes, it will be necessary to adjust the ball 191 toward or from the rotor axis of the motor 194 by means of the screw 192 and altitude scale 194; and this adjustment causes the inverse altitude variation in the an The pilot director 7 For directing the pilot, the bridge 42 (see Figs. 4 and 5) has a transmitter 210 fixed thereto. A pinion 217, fixed to the rotor of the transmitter 216 meshes with a ring gear 217 fixed to the members 33 and 34 of the sight supporting standard. When the sight isrotatedin azimuth, the transmitter 216 operates a repeater 218 in the pilot director P1) to effect rotation of the gear 219. (Figs. 4 and 5.)

The gear 219 meshes with a. gear formed in the hub 220 of a roller supporting spider. The hub 220 is rotatably mounted on ball hearings to rotate about a shaft 221 fixed in a base 222. Each of the arms 223 of the spider has a roller 224 rotatably mounted at its extremity, and these rollers 224 seat in cam grooves 225 formed in the lower face of a friction plate 226, also rotatably mounted on the shaft 221.

The plate 226 has a series of inserts 226 of friction material set therein," and a friction disk 227 rotatable on shaft 221 rests on these inserts. A rod 228 secured to the disk or plate 226 carries an indicator plate 229 at its upper end; and this plate 229 is provided with an indicator line 229', reading against nut 234 threaded thereon to regulate the ten-' sion of the spring 233 for the purpose of normally holding the indicator plate 229 with its mark 229 in alinement with the index mark A plate 235 is journaled on the shaft 221 above the disk 227, and'rests on ball bearings carricd on the upper face of said disk 227. A recessed washer 236 is screwed on to the end of the shaft 221 to regulate the frictional contact between the disk 227 and theinserts 225' on the plate 226. A coil sprin 237, seated in the washer recess, holds the frlction elements normally in yielding contact with each other.

It will be obvious that when the sight 7 2 is rotated in azimuth it will cause the transmitter 216 to operate the repeater 218 and thereby rotate to move the rollers 224 against one or the other of the inclined sides 5 of the cam grooves 225.' This will increase the frictional'contact between the inserts 226 and the friction 'disk 227 to cause rotation of the saiddisk in one direction or theother. I

The spring 237 prevents complete rotation 0 of the disk 227, and returns the disk to zero indicating position just as soon as the Si ht- 72 ceases to rotate in azimuth. The p1 0t director merely steers the craft in the proper directions to keep the indicators 229' and 5 230 in alinement with eachother.

The oifsetis efi'ected by the trail setting of the plate which is clamped in trail or trail angle indicating'position on the bridge 42. The method of automatically 'inclinin the sight 72 to'obtain this oifset and trai corrections is illustrated in Fi s. 2a, 4 and 5. In Figure 2a the arrow X indicates the fore and aft keel'line of the aircraft. It is instrument be. mounted on the craft so t at the common essential that the sightin axis of the trunnions 29 and 30-, andthe cen ter line of brid e 42 lie in a vertical plane containing the keel line of the craft when the latter is in the normal horizontal position of flight. Obviously the bridge 42 must lie fore and'aft of the'eraft, because it carries the trailsetting mechanism, and-trail u must be set in the line of flight.

Assuming now that the instrument is setup in vertical position as shown in Figures 'ment bodily moves t 3, 4 and 5, with sight directed so that its line of sight lies in the vertical plane of the keel line of the craft. In thiscase, the rectanguilar sight-standard suspending base (33, 34, 35, 36) lies in the full line position shown in diagram Figure 2a.

The trail 1" isset off from the center 06 as a starting point by moving the plate 44 to the necessary trail indicating position in slot 43 and byclamping this plate in adjusted position by'the'clamp nut 50. This adjuste members 53 into the.

position shown in full'lines in Figure 2a,

with the common axis of the arm 55 and rod 57 lying-in the vertical plane through the keel line; and with the 'axis of arm 54and .rod 56 perpendicular to this vertical plane.

In this. position, the angle of drift is 0, so that 7 sin a-=r' and rcos a=0.

If new, the craft be started in a bombing operation and eventually assumes the angle of drift a toward the target, it will be obvious that the base frame (33, 34, 35, 36), the member 53, and rods 56 and 57, will assume the position indicated by dotted lines in Figure 2a. Since the center of rotation (axis of pivot pin 52) of the member 53 is fixed by the non-rotatable bridge 42, and is eccentric with respect to center cl of the frame (33 34, 35, 36), it is obvious that the axis of r 57 will be offset from the vertical plane X)! passing throu h the center as and perpendicular to the rame members 35 and 36, and

that this'ofiset will be equal to r sin a. It

will alsobe a parent from Figure 2a that the axis of r 56' will have its original trail settmgrelative totheyertical plane erpendicularto"plane XXand passing't rough the center 0e reduced fromr to r cos a.

It will also be. obvious from Figure 2a that if the angle of drift 1d continues to increase until it reaches a maximum angle of deees, the r sin a ofiset would increase until it became equal to 1 and the 1* cos a timer setting would decrease until it became 0; in

56 would pass which case, the axis of the rod through the center ce.

The scale 46 is calibrated in terms of trail, 1 and its settings bears the same proportion to the actual trail r at ground level as the distance h on the instrument bears to the actual height h of the aircraft above thegrdund. It is evidentfrom the drawing then, that when the rod 57 is ofiset by drift of thej'craft fromthe plane XX it will incline the arm 67 to the left of its position shown in'Figure 3,.displacing the common axis of the bearing 66' and rod 57 through the ofl'set distance 1' sin a, The plane through the line ofsight ofthe telescope and the common axis of bearing 66 (and rod 57) then formsthe hypotenuse side of an imaginary ri ht-angledtriangul'ar prism, the other two si es ofwhich are perpendicular to each all) other and are equal to r sin a and 7t respectively.

'lhus, when the craft is steered in accord ance with the indications of the pilot director as controlled by holding the sight trained on a target, the sight will be maintained in a plane passing through the target and inclined to the vertical at an angle whose tangent is 1' sin a/lt; where it represents the altitude oi the craft, 1' represents the trail of the bomb to be dropped, and 66 represents the angle t drift of the craft toward the target.

it will be noted that the trail is set forwardly of the craft from the center (re-of the instrument. This is necessitated by the fact that the sight is suspended from the base, of its standard. It the sight were supported on the upper face of the base, the trail set ting would be rearward of the craft in the fore and aft direction. a By referring again to Figure 2a, it will be evident that the movements of the slide 59 in the slot 88 will vary as the cosine of the angle ol drift with the perpcndiucular distance between the axis of rod 54 and center 0e equal to 7' cos a; and, since the distance between the axis of the rotor of transmitter T-r and the axis of rod 56 is equal to h the-arm 91 will be inclined to the vertical at an angle whose tangent is r cos'a/h.

What we really do by this trail correcting mechanism is to project the triangle CCD ot'hig. 1 on to the plane EFGH to obtain mechanically the triangle CC'L giving the angular setting of the cosine arm 106 (line JUL) of the timer relative to the ,reference line 107 and also to project this same triangle @C'D on to a vertical plane perpendicular to lane EFGH to give the triangle tl lilll, and consequently, glve the necessary od'setdateral inclination to the optical axis ol the sight.

lo the operation of the device it is merely necessary to set the plate 44 for the trail of the bomb at any desired altitude and airspeed. The bombing operation is then ctliected automatically at all relative speeds, rrom nero to any desired selected maximum relative speed, merely by holding the sight trained on the target and steering the aircralt in accordance with the indications ot' the sight controlled pilotdirector.

l he word aircratt, or its abbreviation cralt, wherever used in this application re- ;l'ers to a dirigible cratt provided with llll@ttl1.3-"@l1gllil3, steering gear, etc.,--tor moving it treely in the airto on point in space indicated by the indicator e ements at my invention which direct the aircraft pilot to perform such necessary operations with his controlling mechanism as may be required to move the'cral t to the point tram which a bomb oil given characteristics must be dropped to strilrc any target upon-which drift. refers to the horizontal angle between the vertical plane including the line of flight of the aircraft and the vertical plane including the concurrent axes of the sighting telescope and the \target on which the telescope is held trained during a bombing op oration. What I claim is y 1. The combination with an aircraft, of bombing apparatus mounted thereon and including: a supportya sight mounted on said support to rotate about intersecting axes; an means operated by the rotations of said sight about said axes, as the result of holding thesight trained on a target, to compensate said apparatus, in the control of the dro ping of bombs from said aircraft, for the iorizontal velocity and drift of the aircraft toward the target.

2. The combination with an aircraft, of bombing apparatus mounted thereon to control the dropping of bombs of known trail angles therefrom and including: a support; a sight rotatable about a horizontal axis on said support; and means, operated as the result of holding the sight trained on a target, to compensate said apparatus, in the control of the dropping of bombs from said aircrafh tor the trail of the bombs and the horizontal velocit of the aircraft toward the taret when t e vertical plane of flight passes through the target.

3. An aircraft, bomb sight apparatus mounted thereon and including: a timer having a straight edge rotatable about an axis in a reference plane representing the vertical plane; and settable trail correcting means connected to said straight-edge for varying the angle of inclination of said straight-edge relative to said reference plane directly as the cosine of the angle of drift of the aircraft toward a target.

4. An aircraft, apparatus'mounted thereon to control the dropping of bombs of known trail angles therefrom and including: i

a sight rotatable about a plurality of axes; a pilot director operable by the rotation of said sight about one of said axes; and means, settable tor trail correction, and operable by holding the sight trained on a target and by steering the aircraft in accordance with the indications of said director as controlled by the trained sight, to maintain the sight with its line at sight rotatable in a plane passing through the target and inclined to the vertical at an angle whose tangent is r sin a/h,

where it represents the altitude of the aircraslt at the instant oil bomb release, r represents thetrail oil the bombs to be dropped, 2 v

and (t represents the angle of drift of the aircraft relative to the target. r

5. An aircraft, apparatus mounted thereon to control the dropping of bombs of known trail angles therefrom and including: I

a sight rotatable about a lurality of axes; a pilot director operable; y the rotation of saldsight about one of said axes; a timer having an arm rotatable toward and from a reference plane representing the vertical plane containing one of said axes and about a fixed axis in said reference plane; and settable trail correcting mechanism connected to said sight and operable by holding the sight trained on a target and by steering the aircraft in accordance with the indications' of said director, as controlled b the trained sight,-to maintain the arm relhtive to said reference plane at an angle whose tangent is 1' cos a/h, where It represents the altitude of the aircraft at the instant of bomb, release, 1' represents the trail of the bombs to be dropped, and a represents the angle of drift of the aircraft relative to the target. I

' on to control the dropping of bombs of known trail angles therefrom and compris ing: a sight rotatable about a plurality of axes; a pilot director operably connected to said sight; a timing instrument having an arm rotatable about an axis in a reference plane representing a vertical plane containmg one of said sight axes and perpendicularly toward and from said reference plane;

' and settable trail correcting mechanism con-j nected to said arm and sight, and operable by holding the sight trained on a target and by steering said aircraft in accordance with 40, the indications of said director as controlled by the trained sight, to maintain the sight with its line of sight rotatable in a plane inclined to the vertical. at an angle whose tangent is r sin ,a/h, and to maintainsaid 5 arm relative to said reference plane at an angle whose tangent is 1' cos a/h, wherem represents the trails of the bombs to, be dro ped, h represents the altitude of the aircra at the instant of bomb release, and a represents the angle of drift of .the aircraft relative to the target.

7. The combination with an aircraft, of bomb sight apparatus mounted thereon and including a rotatable sight, trail correcting mechanism operable to control the dropping of bombs from said aircraft, and means connecting said mechanism to said sight to cause operation of the said mechanism by and in accordance with the movements in azimuth so of the sight relative to the aircraft.

8. Bomb sight apparatus including a support, an arm rotatable about a fixed axis on said support, a contact carrier slidable rectilinearly on said support and slidably and (if: pivotally connected to said arm to be slid aircraft, apparatus mounted therethereb on said support, an electrical contact on sai carrier, and a second electrical con tact mounted on said support in the path of movement of the first named contact.

9. The combination with an aircraft, of a sight mounted thereon to rotate about a plurality of axes, a direction indicator, means connecting said sight to said indicator to operate t e latter solely by the rotations of said sight about one of said axes, and means connected to said sight and operated by the rotation of said sight about other of said axes to cause additional rotation of the sight about the first named axis and transmit movements to said indicator to direct the aircraft in straight line movement horizontally toward and intersecting a vertical line passing through a target on which the sight is held trained only when the planes of flight and track coincide, and to direct the aircraft laterally of said line a definite distance toward the plane of flight when the said planes intersect each other.

10. 'Bomb sight apparatus including: a

sight mounted to rotate about axes perpendicular to each other; a timer havingarms mounted to pivot about a common fixed axis, and means connecting said sight to said arms to rotate said arms independently of each other by the rotations of said sight about its respective axes. 11. The combination with an aircraft, of a bomb sight apparatus mounted thereon and including a movable sight, contacts slidable rectilinearly toward and from each other, and means connecting said contacts to said sight and operable by the movements of said sight for so moving said contacts.

12. An aircraft, bomb sight apparatus mounted thereon and including a sight rotatable about a plurality of axes, a support, a contact carrier slidable rectilinearly on said support, and means including said sight for moving'said carrier'at a speed which varies inversely as the altitude of the aircraft and directly as the horizontal velocity of the aircrafttoward the target on which the sight 1s held trained.

13. An aircraft, bomb sight apparatus mounted thereon and including a sight rotatable about a vertical axis, a support, a slide reciprocable rectilinearly on sa d support, means connecting the sight to said slide and operable by the. rotation of said sightabout said axis to reciprocate the slide on said support, a contact adjustable rectlhnearly on said slide relative to the point of connection of the slide to said means, and mechanism for adjusting said contact relative to said point to vary the distance between said contact and point directly as the square root of the altitude of the aircraft.

14. An aircraft, bomb sight apparatus mounted thereon and including a sight rotatable about a vertical and a horizontal axis,

a support, a slide reciprocable rectilinearly on said support, means connectingthe sight to the slide and operable by the rotation of the sight about its vertical aXis to reciprocate the slide on the support, a contact ad'ustable 'rectilinearly on the slide relative to t e. point or connection of the slide to said means, mechanism for adjusting said contact relative to said point directl as the square root of the altitude of the aircraft, and means controlled by the rotation of the sight about its horizontal axis for varying the adjusted position of said contact directly as the horizontal velocity of the aircraft toward a target on which the sight is held trained.

15. An aircraft, bombing apparatus mounted thereon and including a target sight rotatable about a vertical axis, a pilot director having a reference mark fixed relative to said aircraft and having an indicator movable in opposite directions past said mark, means for yieldingly urging said indicator into alinement with said mark, and means oper able by the rotations of said sight about said axis to cause displacement of said indicator relative to said mark. in proportion to the speed of rotation of the sight.

16. Bomb sight apparatus having a timer including; a support a screw rotatable about its axis on said support; means for rotating said screw at variable speeds; a contact carrier slidable rectilinearly on said support parallel to the axis of said screw; a gear rotatable on said carrier and in mesh with said screw; movable means for sliding said carrier on said support at variable speeds; and mechanism controlled by variations in the movements of the last named means relative to said carrier to vary the speed of rotation of said screw and cause the gear to slide, without rotation,

in said carrier along said screw.

17. An instrument having a pointer rotatable in opposite directions thereon, a gear rotatable concentrically with said pointer and having electrical contacts spaced slightly apart thereon and separated by a strip of insulation, a contact fixed to said pointer and slidable over said strip and electrical contacts, and a reversible motor connected in circuit with said contact and contacts and having a gear fixed to its rotor and in mesh with the first named gear.

18. in bomb sight apparatus, the combination with a support, a sight standard rotatable thereon, a timing instrument including a contact carrier, a contact slidable on said carrier, and means connecting saidstandard and contact for slidingthe carrier by the rotation. of the standard.

19. in bombing apparatus, the combination of a sight mounted to rotate about axes perpendicular to each other, with a timer having two arms pivoted to rotate about a common aais, means to rotate one of said arms in synchronism with the rotation of said sight about one of said axes, and means to rotate the other arm in synchronism with the rotation of the sight about the other of said axes.

20. In combination. with an aircraft, bombing apparatus mounted thereon and including a sight, means for mounting said sight to rotate about a plurality of axes, a fixed support, a contact slidable rectilinearly onv said support, an arm pivoted to said support and connected slidably and rotatably to said contact, and means connectingsaid arm and said sight to rotate said arm and maintain it constantly at the same angle to the path of slide of said cont-act as the line. of sight makes with the" horizontal.

21. The combination With an unstable platform of a standard 'rotatably mounted on said platform; a trunnion member rotatable on said standard; a bearing rotatable with, 3 and about an axis'perpendicular to, said member; a support rotatable in said bear-.

ing about an axis perpendicular to the bearing axis; a sight fixed in said support, the axes of said member, bearing and support being concurrent; andmeans for oscillating said sight about said concurrent axes, to hold the sight with its line of sight rotatable a plane inclined to the vertical.

22. In combination with an aircraft, a

support rotatableabout a Vertical axis, a sight rotatable on said suplport, asteering indicator having a member xed to said aircraft and a member movable relatively thereto, means connecting said support and movtimer to said standard and sight to transmitthe rotations of said sight and standard about their respective axes to said timer to operate the tuner, and means connecting said standard to said indicator to operate the said in dicator by "rotation of said standard about its axis.

24. the combination with an aircraft, of

bombing apparatus including a timer controllint the dropping of bombs from said aircraft, a steering indicator, a sight mounted to rotate about two axes, means connecting the sight to said indicator to operate the latter by the rotation of the sight about one of said axes, and means connecting the said sight to all lam

the timer to operate the timer by the rotation of the sight about both of said axes.

25. The combination with an aircraft, of bomb sight apparatus mounted thereon and comprising a sight standard rotatable about a normally vertical axis, a sight rotatable on said standard, a timer including a pivoted trail correcting arm, a pilot director, means connecting the said director and said arm to said standard for operation by the rotation of said standard about said vertical axis.

26. A sighting instrument including a support, a standard rotatable about an axis per- 'pendicular to said support, a trunnion rotatable in said standard; about an axis perpendicular to the first named axis, a sight carrier rotatably mounted-in said trunnion, and a sight rotatable about its line of sightin said carrier, the line of 'sightandthe axis of rotation of said carrier and said trunnion axis being concurrent.

27 A sightinginstrument including a support, a standard rotatable about an axis perpendicular to said support, a trunnion .rotatable in said standard about an axis perpendicular to the first named axis, a sight carrier rotatably mounted in said trunnion,-a sight rotatable about its line of sight in said carrier, the line of sight and the axis of rotation of said carrier and said trunnion axis being eoncurrent, and means for rotating said sight about its line of sight. I

28. A sight, means for mounting said sight to rotate about four concurrent axes, and means controlled by the rotation of the sight about one of said axes and for moving the sight about its remainin axes to maintain the sight with its line of sig t inclined to the vertical.

bomb sight apparatus mounted thereon and including a timer having a pivoted trail correctin arm, and a trail correcting indicator settable to cause said arm to vary its angular trail correcting movements about its pivot as the cosine of the angle of drift of the aircraft while drifting in straight line movement to ward a target in which the sight is held trained.

In testimony whereof I have signed in name to this specification.

. JOSEPH 'DUGAN.

'29. In bomb sight apparatus, a sight rotatable about a horizontal axis and a vertical axis, a support, an arm rotatable in said support about a fixed axis thereon, means connecting said arm to said sight to rotate the arm about said fixed axis and maintain it at the same angle to a reference line passing through said fixed axis as the line of sight makes with the vertical, a trail arm rotatable about said fixed axis, and means connecting said sight to said trail arm to rotate the latter in sync ronism with the rotations of the sight about its vertical axis and including means- 

